<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Bootstrap环境搭建模板</title>
    <link rel="stylesheet" href="./bootstrap-3.4.1-dist/css/bootstrap.css">
    <script src="./bootstrap-3.4.1-dist/js/jQuery1.12.4.js"></script>
    <script src="./bootstrap-3.4.1-dist/js/bootstrap.js"></script>
</head>

<body>
    <style>
        div[class^=col-md] {
            border: 1px solid red;
            
        }
    </style>
    <div class="container-fruid">
        <div class="row">
            <div class="col-md-9">
                level 1: .col-md-9
                <div class="row">
                    <div class="col-md-6">level 2: .col-md-1</div>
                    <div class="col-md-6">level 2: .col-md-1</div>
                </div>
            </div>
            <div class="col-md-3">col-md-3</div>
        </div>
    </div>
</body>

</html>